It turns out that importing an MP4 file shot by a Flip camera to FCP is not as intuitive as I thought it might be. For a while everything was running smoothly but, as my editing advance to about the 2-minute point, the audio went out of synch by approximately 3-4 frames. That gave my the clue that I had a discrepancy between 30 and 29.97 fps. But, I had set my sequence to 30fps to match the raw footage I had imported. So what was going on? What I was doing wrong?
Together with Kenneth Chan at Meyer Library we were able to figure it out.
The video that Flip generates is MP4 1280x720 at 30fps as the QuickTime 7 Inspector shows:
When I imported the raw footage to FCP, I set the sequence accordingly. But it turns out that the frame rate can be set to either 30fps or 29.97fps. As you can see, my choice was 29.97.
The critical step comes when you place the clip in the timeline. At this point, FCP displays the following warning that includes two alternatives.
My choice was to click Yes. The result was losing audio sync. It turns out that the correct choice is to select No.
This is it.
You still have to render the sequence, both video and audio. Once this is done, you are ready to edit.